Research On Arc-suppression Coil Tuning Method And Optimized Control Scheme

Currently, in our country, distribution networks’s neutral point always earthed viaArc-suppression Coil or ungrounded. According to the tuning methods, arcsuppression-coil can be divided into pre-tuning and unpre-tuning, and according to thecompensation degree of Arc-suppression Coil to capacitance current,Arc-suppressionCoil has three working models:full compensation, overcompensation andundercompensation.While the existing Arc-suppression Coil only can compensatereactive component of the ground fault current. Thus, for the insulation aging,overhead lines and the larger grid, it’s necessary to measure the insulation resistance.Actual operation, the neutral displacement voltage is prevalent, especially theover-voltage when Arc-suppression Coil full compensation, and the larger the neutralpoint displacement voltage, the more harmful for safe operation of the system, soincreasing the damping rate or resonance degree is need. However, the currentzero-sequence voltage suppression method only gives a rough precision, not gives theprecisely controlled condition, and not analyses the changing damping rate’s affect toneutral voltage track. Single-phase ground fault often accompanied by a transitionresistance, transition resistance can weaken fault feature, reduce the sensitivity of theprotection device.To remedy the existing mechod of suppressing neutral displacement voltage inresonant earthed system, the optimal control condition for the degree ofdeviating-from-resonance and the damping ratio under normal operation of powergrid are proposed. To implement accuracy tracking and control of zero-sequencevoltage, the locus of zero-sequence voltage under different degree ofdeviating-from-resonance of immediately adjusted Arc-suppression Coil and thatunder different damping ratio of preset Arc-suppression Coil are analyzed. Accordingto insulation parameters of power grid and zero-sequence voltage value under presentimpedance of Arc-suppression Coil branch, the accurate control condition to suppressneutral displacement voltage can be calculated. For parallelled dampingArc-suppression Coil, based on the change in the zero-sequence voltage can judge thecompensation state when change the parallelled damping.Raise a new method named new type of automatic tuning Arc-suppression Coilbased on detuning, this method enables tracking and measuring capacitive current,this can only be used in parallelled damping arc suppression-coil. Raise a new method named automatic Arc-suppression Coil compensation technology based on paralleldamping resistor, this method can not only measure the capacitive current accuratelybut also can measure the total resistance of the insulation grid. Raise a generalautomatic tuning method of change parameters Arc-suppression Coil compensationdevice, it could be used in the control of a followed resonant or pre-resonantArc-suppression Coil.Respectively, for ungrounded and resonant grounding grid, according to thedisplacement of the neutral point voltage determines the transition resistance after asingle-phase ground fault.Finally, simulate the neutral point voltage control method and Arc-suppressionCoil tuning control methods. Simulation results have proved the correctness andvalidity of the theory.